This invention relates to cyanoacrylate adhesives, and more particularly to cyanoacrylate adhesives which are solid at room temperature and are able to liquefy at higher than room temperature and to polymerize to form adhesive bonds or adhesive coatings. The adhesive compositions are in a form, which is particularly easy to be applied in industrial or consumer applications, as well to skin or living tissue. The adhesives are useful in bonding or coating of metals, plastics, wood, rubbers, composite materials, and living tissue. They are also useful in medical applications, including but not limited to, wound and surgical incision closure, medical device fixation, sealants and void fillers, embolic agents and other general medical applications. The invention also relates to the method of obtaining the solid cyanoacrylate compositions and to the method of delivering a solid cyanoacrylate adhesive composition to one or more substrates by the means of a suitable dispenser, joining two or more substrates together and bringing the them to a temperature above room temperature, if the substrates are not already at a temperature above room temperature, which transforms the adhesive into a liquid form, whereby the adhesive polymerizes to form a strong adhesive bond. The invention further relates to the method of delivering a solid cyanoacrylate adhesive composition by means of a suitable dispenser to a substrate where the solid adhesive transforms itself into a viscous liquid under the influence of the temperature of the substrate and polymerizes to form a coating. The invention also relates to suitable dispensers for solid cyanoacrylate adhesives.
Liquid cyanoacrylate compositions have long been known in the art as excellent adhesives. They have found wide application as industrial and structural adhesives. They have also found wide application in the consumer market for repair of household items and in the hobby sector for assembly and repair. Due to their unique ability to bond living tissue, liquid cyanoacrylate compositions have found application in medicine for closing wounds and incisions, especially in cases where suturing does not provide satisfactory results. Cyanoacrylate compositions have also found life-saving application for embolization of arterio-venous malformations and aneurysms.
One of the major disadvantages for all of the above applications is the low viscosity of the adhesives. Their runniness requires either special dispensing equipment or particular skill and training of the user for their proper administration.
A variety of attempts have been made to overcome the known disadvantages that result from the runniness of cyanoacrylate adhesive compositions. Various polymer additives have been disclosed to adjust the viscosity of cyanoacrylate preparations. In this regard, please refer to U.S. Pat. Nos. 2,765,332; 2,794,788; 3,527,841; 3,282,773; 3,692,752; 3,836,377; 4,038,345; and 4,102,945, the teachings each of which are incorporated by reference in their entirety. The polymer additives discussed, however, have not satisfactorily resolved the runniness related disadvantages since only relatively minor adjustments to the viscosity are achieved and in some cases the proposed additives interfere with the quality of the adhesive bond.
Others have attempted to increase the viscosity of cyanoacrylate adhesive preparations by modifying the cyanoacrylate itself and/or by adding modified cyanoacrylates to the adhesive composition. For example, U.S. Pat. No. 3,564,078 discloses the use of poly (ethyl 2-cyanoacrylate) as a component of cyanoacrylate compositions. However, these compositions have also proven to be unsatisfactory solutions to these problems.
The use of fillers has also been proposed as a method for adjusting the viscosity of cyanoacrylate preparations. According to U.S. Pat. No. 4,105,715, finely divided organic powders such as polycarbonates, polyvinylidene fluorides, polyethylenes, and other polymeric powders are proposed as additives for cyanoacrylates. U.S. Pat. Nos. 3,663,501; 3,607,542; 4,533,422; and Re. 32,889 propose the addition of various inert inorganic materials such as silica, quartz, alumina, calcium and metal salts to cyanoacrylate preparations as fillers. Again, although these additives can form thixotropic compositions, they are generally unsatisfactory to resolve the runniness problem since they provide relatively ineffective adjustments to viscosity and have a tendency to interfere with the quality of the bond.
In addition to runniness, the stability and shelf life of cyanoacrylate adhesive preparations can also be less than optimum, particularly when some of the foregoing additives are used. A series of U.S. patents comprising U.S. Pat. Nos. 5,514,371; 5,514,372; 5,532,867; 5,575,997; 5,582,834; and 6,203,802 describe the inclusion of certain formaldehyde scavengers in the cyanoacrylate composition. These formaldehyde scavengers can be encapsulated in microcapsules comprised of polycaprolactone.
Although the above cited art has suggested methods for altering the viscosity of cyanoacrylate preparations, they have either achieved relatively moderate viscosity increases such that the preparations remain runny or they have created thixotropic cyanoacrylate adhesives which produce less desirable bonding characteristics. Thus, the need remains for a cyanoacrylate adhesive preparation which is not runny and has the excellent bonding characteristics of typical cyanoacrylates. It is an object of this invention to produce cyanoacrylate adhesive compositions which solve the runniness problem while at the same time provide the excellent bonding characteristics of typical cyanoacrylates.
The current invention provides a cyanoacrylate adhesive composition which is in a new undiscovered form. The adhesives of the present invention are preferably in a solid form at room temperature and below room temperature. Room temperature is considered the interval from about 15xc2x0 C. to about 37xc2x0 C., and more preferably from about 15xc2x0 C. to about 25xc2x0 C. This makes the application of the adhesive very easy and well controlled. The application is similar to applying other solid non-cyanoacrylate adhesives molded in a stick-shape. Containers similar to the ones used to store and apply solid non-cyanoacrylate adhesives, wherein the adhesives is contained in a stick shape and is controllably pushed out of the container, are deemed suitable for storage and application of the adhesives of the present invention. Rubbing the adhesive of the present invention onto the surface to be coated or bonded deposits the required amount of the adhesive. The adhesive is preferably activated when the temperature of the substrate reaches a temperature above room temperature, which temperature renders the adhesive in liquid form. The liquefied adhesive spreads and wets the underlying substrate surface and can polymerize as a typical cyanoacrylate adhesive. The joint assembly can be made before or after the liquification of the adhesive. Assembly before liquification of the adhesive can be particularly advantageous. The liquidification and polymerization of the adhesive can be induced by bringing the joint to a temperature above room temperature, i.e., to temperature higher than 25xc2x0 C. and preferably higher than 30xc2x0 C. Industrially the necessary heating can be achieved by any of the known means of heating by thermal, IR, UV or microwave radiation. In the home repair environment or hobby model building environment the necessary heating can be achieved by simply holding the joint between one""s fingers or hands, with body heat being sufficient to liquefy the adhesive and initiate its polymerization. When the adhesive composition of the present invention is used as a coating the same procedure applies as heat generated by contact with the body or by thermal, IR, UV or microwave radiation in industrial applications is used to liquefy the adhesive composition, rendering it easily polymerizable.
These properties of the cyanoacrylate compositions of the present invention make it especially suitable for use in medical applications. After controlled and easy application onto skin or other living soft or hard tissue, the adhesives quickly liquefy and bond the surfaces or form an adhesive coating. Sterilization of these solid cyanoacrylate adhesive compositions, when used in medicine, is advantageous and the method taught in UK Patent GB 2306469 is particularly suitable and is incorporated herein by reference. The solid cyanoacrylate compositions of the present invention can contain a biodegradable or bioabsorbable component. The bioabsorbable cyanoacrylate compositions described in U.S. Pat. No. 6,224,622 are particularly suitable for inclusion into the solid cyanoacrylate adhesives of the present invention, which patent is incorporated herein by reference. Medical applications of the adhesives of the present invention include, but are not limited to, wound closure (including surgical incisions and other wounds), adhesives for medical devices (including implants), sealants and void fillers in human and animal medical application, and embolic agents.
One embodiment of the present invention is directed to a method for making a cyanoacrylate adhesive composition which is in a solid form at room temperature by dissolving into a cyanoacrylate monomer or a mixture of cyanoacrylate monomers one or more solidifying polymers or copolymers at elevated temperature, then leaving the solution for a sufficient period of time at room temperature or below room temperature to form a solid at room temperature. The cyanoacrylate monomers are preferably selected from the group consisting of alkyl 2-cyanoacrylates, alkenyl 2-cyanoacrylates, alkoxyalkyl 2-cyanacrylates, and carboalkoxyalkyl 2-cyanoacrylates. The alkyl group of the one or more cyanoacrylates preferably has 1 to 16 carbon atoms. The solidifying polymer or copolymers is preferably but is not limited to, poly (xcex5-caprolactone).
Another embodiment is directed to a solid cyanoacrylate adhesive composition made by this method. A further embodiment is directed to a solid cyanoacrylate adhesive composition which forms a bioabsorbable adhesive. Another embodiment is directed to containers suitable for storage and dispensing of the solid cyanoacrylate adhesive composition in this invention. Yet another embodiment of this invention is the method of applying a cyanoacrylate adhesive composition in solid form, liquefying it and curing it to form an adhesive bond or adhesive coating. A further embodiment of the present invention is the use of the solid cyanoacrylate adhesive compositions for joining and coating in industrial, consumer and medical (including surgical) applications. Other embodiments and advantages of the invention are set forth in part in the description which follows, and in part, will be obvious from this description, or may be learned from the practice of the invention.